|
| |
|
|
A139268
|
|
Twice nonagonal numbers (or twice 9-gonal numbers): n(7n-5).
|
|
2
| |
|
|
0, 2, 18, 48, 92, 150, 222, 308, 408, 522, 650, 792, 948, 1118, 1302, 1500, 1712, 1938, 2178, 2432, 2700, 2982, 3278, 3588, 3912, 4250, 4602, 4968, 5348, 5742, 6150, 6572, 7008, 7458, 7922, 8400, 8892, 9398, 9918, 10452, 11000
(list; graph; refs; listen; history; internal format)
|
|
|
|
OFFSET
| 0,2
|
|
|
LINKS
| Index entries for sequences related to linear recurrences with constant coefficients, signature (3,-3,1).
|
|
|
FORMULA
| a(n) = A001106(n)*2 = 7*n^2-5*n = n(7n-5).
a(n)=14*n+a(n-1)-12 (with a(0)=0) [From Vincenzo Librandi (vincenzo.librandi(AT)tin.it), Aug 03 2010]
|
|
|
EXAMPLE
| a(1)=14*1+0-12=2; a(2)=14*2+2-12=18; a(3)=14*3+18-12=48 [From Vincenzo Librandi (vincenzo.librandi(AT)tin.it), Aug 03 2010]
|
|
|
MATHEMATICA
| s=0; lst={s}; Do[s+=n; AppendTo[lst, s], {n, 2, 6!, 14}]; lst [From Vladimir Orlovsky (4vladimir(AT)gmail.com), Apr 02 2009]
|
|
|
CROSSREFS
| Cf. A001106.
Sequence in context: A131538 A009820 A126909 * A052681 A048910 A077591
Adjacent sequences: A139265 A139266 A139267 * A139269 A139270 A139271
|
|
|
KEYWORD
| easy,nonn
|
|
|
AUTHOR
| Omar E. Pol (info(AT)polprimos.com), May 15 2008
|
| |
|
|
